AJAX Poll

Example Explained The HTML Page

When a user choose an option above, a function called "getVote()" is executed. The function is triggered by the "onclick" event:

Example:

<html>

<head>

<script type="text/javascript">

function getVote(int)

{

if (window.XMLHttpRequest)

  {// code for IE7+, Firefox, Chrome, Opera, Safari

  xmlhttp=new XMLHttpRequest();

  }

else

  {// code for IE6, IE5

  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");

  }

xmlhttp.onreadystatechange=function()

  {

  if (xmlhttp.readyState==4 && xmlhttp.status==200)

    {

    document.getElementById("poll").innerHTML=xmlhttp.responseText;

    }

  }

xmlhttp.open("GET","poll_vote.php?vote="+int,true);

xmlhttp.send();

}

</script>

</head>

<body>



<div id="poll">

<h3>Do you like PHP and AJAX so far?</h3>

<form>

Yes:

<input type="radio" name="vote" value="0" onclick="getVote(this.value)" />

<br />No:

<input type="radio" name="vote" value="1" onclick="getVote(this.value)" />

</form>

</div>



</body>

</html>

The getVote() function does the following:

    * Create an XMLHttpRequest object
    * Create the function to be executed when the server response is ready
    * Send the request off to a file on the server
    * Notice that a parameter (vote) is added to the URL (with the value of the yes or no option)

The PHP File

The page on the server called by the JavaScript above is a PHP file called "poll_vote.php":

Example:

<?php

$vote = $_REQUEST['vote'];



//get content of textfile

$filename = "poll_result.txt";

$content = file($filename);



//put content in array

$array = explode("||", $content[0]);

$yes = $array[0];

$no = $array[1];



if ($vote == 0)

  {

  $yes = $yes + 1;

  }

if ($vote == 1)

  {

  $no = $no + 1;

  }



//insert votes to txt file

$insertvote = $yes."||".$no;

$fp = fopen($filename,"w");

fputs($fp,$insertvote);

fclose($fp);

?>



<h2>Result:</h2>

<table>

<tr>

<td>Yes:</td>

<td>

<img src="poll.gif"

width='<?php echo(100*round($yes/($no+$yes),2)); ?>'

height='20'>

<?php echo(100*round($yes/($no+$yes),2)); ?>%

</td>

</tr>

<tr>

<td>No:</td>

<td>

<img src="poll.gif"

width='<?php echo(100*round($no/($no+$yes),2)); ?>'

height='20'>

<?php echo(100*round($no/($no+$yes),2)); ?>%

</td>

</tr>

</table>

The value is sent from the JavaScript, and the following happens:

   1. Get the content of the "poll_result.txt" file
   2. Put the content of the file in variables and add one to the selected variable
   3. Write the result to the "poll_result.txt" file
   4. Output a graphical representation of the poll result

AJAX Poll

Example Explained The HTML Page

The PHP File

Web Tutorials